--

-- This module implements {{Pop density}}

--

local p = {}

local math_module = require( "Module:Math" )

local precision = math_module._precision

local sortkey = require( "Module:Sortkey" )



local function rnd(num, digits)

	-- This function implements {{rnd}}

	return math_module._precision_format(tostring(num), tostring(digits))

end

local unitnames = {

	"km²" = "km2",

	"sqkm" = "km2",

	"km2" = "km2",

	"mi2" = "sqmi",

	"sqmi" = "sqmi",

	"acres" = "acre",

	"acre" = "acre",

	"ha" = "ha",

	"dunam" = "dunam",

	"m²" = "m2",

	"sqm" = "m2",

	"m2" = "m2"

}

local unitmult = {

	"km2" = 1000000,

	"sqmi" = 2589988.110336,

	"acre" = 4046.8564224,

	"ha" = 10000,

	"dunam" = 1000,

	"m2" = 1

}

local unitstr = {

	"km2" = 'km<sup>2</sup>',

	"sqmi" = 'sq&nbsp;mi',

	"acre" = 'acre',

	"ha" = 'ha',

	"dunam" = 'dunam',

	"m2" = 'm<sup>2</sup>'

}



local function popdensity(pop, area1, areaunit1, areaunit2, prec, disp, flip)

	local dens1, dens1sort, prec1

	local dens2, dens2sort, prec2

	local str1, str2 = '', ''

	local uniterror = '<sup>[[Template:Pop density|?Unknown unit?]]</sup>[[Category:Pop density using unsupported units]]'

	

	if(pop ~= '' and area1 ~= '') then

		-- pop and area are defined

		local popnum = tonumber(pop)

		if not popnum then

			error(string.format('Unable to convert population "%s" to a number', pop), 2)

		end

		local area1num = tonumber(area1)

		if not area1num then

			error(string.format('Unable to convert area "%s" to a number', area1), 2)

		end

		local dens1num = popnum/area1num

		

		local unit1 = unitnamesareaunit1 or nil

		local unit2 = unitnamesareaunit2 or nil

		

		prec1 = (prec ~= '') and tonumber(prec) 

			or (1+math.log10(2*area1/(1/10^precision(pop)+pop/area1/10^precision(area1))))

		dens1 = rnd(dens1num, math.floor(prec1 + 0.5))

		dens1sort = '<span style="display:none" data-sort-value="'

			.. sortkey._sortKeyForNumber(dens1num) .. '♠"></span>'

		if (unit1) then

			str1 = '/' .. unitstrunit1

			if(unit2) then

				-- convert

				local mult = unitmultunit2/unitmultunit1

				prec2 = prec1 - math.log10(mult)

				dens2 = rnd(dens1num*mult, math.floor(prec2 + 0.5))

				dens2sort = '<span style="display:none" data-sort-value="'

					.. sortkey._sortKeyForNumber(dens1num*mult) .. '♠"></span>'

				str2 = '/' .. unitstrunit2

			elseif(areaunit2 ~= '') then

				if( disp ~= 'num' ) then

					dens2 = '?'

				else

					dens2 = '?' .. uniterror

				end

				str2 = '/' .. areaunit2 .. uniterror

			end

		elseif(areaunit1 ~= '') then

			if( disp ~= 'num' ) then

				dens2 = '?'

			else

				dens2 = '?' .. uniterror

			end

			if(unit2) then

				str2 = '/' .. unitstrunit2

			elseif(areaunit2 ~= '') then

				str2 = '/' .. areaunit2 .. uniterror				

			end

			str1 = '/' .. areaunit1 .. uniterror

		end



		-- form output

		if( str2 ~= '' ) then

			-- has a converted unit

			if( disp ~= 'num' and disp ~= 'table' ) then

				-- display input and output density numbers with units

				if( flip == 'on' ) then

					return (dens2sort or '') .. dens2 .. str2 .. ' (' .. dens1 .. str1 .. ')'

				else

					return (dens1sort or '') .. dens1 .. str1 .. ' (' .. dens2 .. str2 .. ')'

				end

			elseif( disp == 'table') then

				dens1 = (dens1sort or '') .. dens1

				dens2 = (dens2sort or '') .. dens2

				return pop .. '||' .. area1 .. '||' .. dens1 .. '||' .. dens2

			else

				-- display output density number without unit

				return dens2

			end

		else

			-- no converted unit

			if( disp ~= 'num' and disp ~= 'table' ) then

				-- display input density number with unit 

				return (dens1sort or '') .. dens1 .. str1 

			elseif( disp == 'table') then

				return pop .. '||' .. area1 .. '||' ..(dens1sort or '') .. dens1

			else

				-- display input density number without unit

				return dens1

			end

		end

	end

	return ''

end



function p.density(frame)

	local args = (frame.args3 ~= nil) and frame.args or frame:getParent().args

	return popdensity(

		args1 or '', args2 or '', args3 or '', args4 or '', 

		args'prec' or '', args'disp' or '', args'flip' or ''

		)

end



return p